1. Field of Invention
The present invention relates to a light emitting device circuit and a control method thereof; particularly, it relates to such light emitting device circuit and control method thereof with a remote control circuit.
2. Description of Related Art
FIG. 1 shows a schematic diagram of a light emitting diode (LED) driver circuit 100. The LED driver circuit 100 is for driving an LED circuit 10. As shown in FIG. 1, the LED driver circuit 100 includes an LED control circuit 110, a remote control circuit 120, and a voltage supply circuit 130. The LED control circuit 110 is controlled by a control signal, to convert an input voltage Vin to an output voltage Vout which is supplied to the LED circuit 10. The remote control circuit 120 receives electrical power (supply voltage) from the voltage supply circuit 130, and generates the control signal according to a remote signal such as a radio frequency (RF) signal, a power line communication (PLC) signal or an infrared (IR) signal. The voltage supply circuit 130 converts the input voltage Vin to the supply voltage to supply electrical power to the remote control circuit 120.
The remote control circuit 120 should keep active even when the LED control circuit 110 is turned OFF the LED circuit 10, such that the remote control circuit 120 can receive the remote signal and generate a corresponding control signal during when the LED circuit 10 is OFF. To this end, the voltage supply circuit 130 should keep generating the supply voltage, such that the remote control circuit 120 can operate regardless whether the LED circuit 10 is ON or OFF. In the prior art LED driver circuit 100, the voltage supply circuit 130 receives the input voltage Vin and converts it to the supply voltage. However, the input voltage Vin is usually a relatively high voltage such as rectified power from 110V or 220V AC, so the supply voltage circuit 130 needs to be a circuit which is capable of sustaining the high input voltage, and because of safety regulation it often requires using a high voltage isolation structure which significantly increases the cost, and the circuit is more vulnerable because it operates in a high voltage environment.
To overcome the drawbacks in the prior art, the present invention proposes a light emitting device driver circuit and a control method wherein the voltage supply circuit has a relatively lower manufacturing cost; the voltage supply circuit can provide the supply voltage regardless whether the LED circuit is ON or OFF, but is not directly connected to the high input voltage Vin.